The present disclosure generally relates to devices used in bone surgery, and more particularly, relates to a bone anchoring device.
U.S. Pat. No. 5,443,467 discloses a bone screw comprising a receiver member and a screw member having a threaded portion and a head. A pressure disk is slidable within the receiver member and acts onto the head. The rod is placed on top of the pressure disk and the arrangement is locked by means of a rod locking nut and a lock nut exerting pressure onto the rod which then exerts pressure on the pressure disk, thus locking the head.
U.S. Pat. No. 6,063,090 discloses a spinal fixation system with a pedicle screw and a retainer head to connect the pedicle screw with a longitudinal support. An insert is provided with exerts a pressure onto the head of the pedicle screw which is accommodated in the retainer head. Tension means are provided to press onto the insert to lock the head of the pedicle screw in its polyaxial position and to fix the longitudinal support. Depending on the insert and the tension means the rod and the head of the bone screw may be separately fastened.
US 2003/0100896 A1 discloses an element with a shank and a holding element connected to the shank for connecting to a rod. The holding element has a recess having a U-shaped cross-section for receiving the rod with two open legs and an inner thread on the open legs and a locking element with an outer thread which cooperates with the inner thread of the legs. In one embodiment, the holding element is polyaxially connected with the head of a bone screw. To lock the head in its polyaxial position a pressure disk is provided which acts on the head when pressure is exerted onto the rod by means of an inner screw. In another embodiment the head can be locked independently from the fixation of the rod. If the two types of anchoring devices are to be used simultaneously during surgery it is necessary to have the different types of anchoring devices separately on stock or to pre-assemble the preferred anchoring device with the required pressure disk and/or the pressure element before or during surgery.
US 2004/0186473 discloses a bone anchoring device with a bone anchoring element which is polyaxially connected to a receiving portion and a pressure element to exert pressure onto the head to lock the head in its position wherein an inner screw is provided which can be screwed in the receiving portion to exert a pressure on the rod. The inner thread ends above the rod when the rod is inserted and an undercut is provided to allow a design of the receiving portion to be smaller in its dimensions.
In view of the above, there is a need for a bone anchoring device that can remedy one or more of the above described problems associated with current bone anchoring devices.